Collect. Czech. Chem. Commun.
1996, 61, 951-956
https://doi.org/10.1135/cccc19960951
Kinetics of Coupling of 4-Methoxybenzenediazonium Ion with 2,6-Dihydroxypyridine
Jaroslava Horáčkováa and Vojeslav Štěrbab
a Department of Organic Technology, University of Pardubice, 532 10 Pardubice, Czech Republic
b Department of Organic Chemistry, University of Pardubice, 532 10 Pardubice, Czech Republic
Abstract
The kinetics of reaction of 4-methoxybenzenediazonium ion (3) with 2,6-dihydroxypyridine (1) has been studied in methoxyacetate, acetate, and phosphate buffers. The rate-limiting step is the formation of the reaction intermediate and not the splitting off of the proton (which was detected in the cases of citrazinic acid and its methyl ester). Therefrom it follows that for 2,6-dihydroxypyridine derivatives the steric hindrance to the formation of the Wheland intermediate exerted by CO2- and CO2CH3 groups represents a necessary condition for the rate-limiting splitting off of the proton and, hence, for the existence of general base catalysis.
Keywords: Chemical kinetics; Azo coupling reaction; Electrophilic aromatic substitution; Dissociation constant.
